...how does one get into this seriously? From seeing a few shows, I've seen magicians with really elaborate and awe inspiring tricks do some really incredible looking things.
You have to crawl before you can walk. Get a copy of Mark Wilson's Complete Course in Magic. It is a huge book at a great price and will give you an excellent grouding in magic.
Keep in mind, how incredible anything looks is directly proportional to the magician's ability to present what he does with showmanship. What I'm saying is that a little "nothing" trick in the right hands can be a miracle and a miracle in the wrong hands can be a little "nothing" trick. It's up to you to make magic, well, magic.
Does it work primarily as a master/apprentice thing, as far as tricks go?
It can. If you get lucky enough to find a mentor, it will speed up your learning process. However, it is not a requirement. Your first step, though, should be to get the book that I suggested above.
If you have a local magic group (IBM, or another) you may wish to look into that. Hopefully, you have a magic shop close and they will be able to assist you in finding any local clubs.
Now, clubs can be good or bad - it depends on the members. I've heard just as many bad stories about local clubs as I've heard good ones. So, whether or not you join will be a matter of if you like the folks that are in the group or not. Don't feel that you are required to be in a club if you don't want to be or if you don't feel welcomed there.
Do many magicians create their own right away, as a way to get started? (this seems challenging to me) Or perhaps do people go to conventions or something to learn?
Well, you've taken the first step, haven't you? You've joined an internet group and asked for help in finding a your way. There is neither a right way nor a wrong way.
Browse these pages and read all the threads that catch your eye. You'll find a great deal of good advice on different areas of magic as well as presentational hints and tips and so much more. Again, I can't impress upon you enough that it's not the trick that makes the magic, it's the performer doing the trick that makes or breaks it.
Furthermore, the magic industry is a vast wasteland of stuff that they'll try to sell you as the next greatest miracle. Be very careful when deciding to buy these things. One of the pleasures that you'll find is buying nifty stuff to play with, but you have to be careful or you'll also find your credit cards maxed out...You don't want that to happen. Peruse the reviews area of this site and the many others that are out there on the internet.
Conventions are a great way to meet other magicians with all sorts of different skill levels and get advice from the pros who are lecturing. Yes, go to conventions.
So, take that first step and get yourself a copy of Wilson's book. You won't regret that.
Now, for the next step:
Wilson's covers a huge array of magic fields between the covers - Cards, coins, rope, impromptu and more...Even stage illusions.
Pick out a few tricks that you really like and want to learn, then learn them! But, put the time into them before you show them. Make sure that you have them down 100%, backward and forward. One of the main things that stops a beginner magician is that they get caught and it's a bad feeling to get caught. After that, they don't want to do magic anymore. So, make sure that you have it down 100% and you don't get caught.
You'll find that you'll gravitate toward one particular kind of magic that you will probably want to specialize in. It may be cards, it may be coins, it may be ropes and it may even be stage illusion. This is where you should put the bulk of your time and money into. If cards, then pick up a copy of "The Royal Road to Card Magic" (Hugard & Braue). If coins, then pick up a copy of "Modern Coin Magic" (Bobo).
(There are those who will suggest that the books above are not your best choices, so when you're ready to invest in a book or DVD that you'd like to start learning from then post again and get some other opinions...Then, make your choice!)
I suggest that you spend 90% of your time working on the specialized field of your choice, but still set aside 10% of your time to work on other stuff because you should at least be well rounded.
Keep posting for advice when you need to and feel free to jump in where you're comfortable.
Best wishes on your new road.
Mike.